Process for the preparation of 7-aminocephalosporanic acids

ABSTRACT

7-Aminocephalosporanic acid (7-ACA) and 7-amino-3-methyl-3-cephem-4-carboxylic acid (7-ADCA) are valuable intermediates in the preparation of semi-synthetic cephalosporins. These compounds are commonly prepared by cleaving the amide bond of compounds having the formula ##SPC1## 
     In which R 6  is H or ##EQU1## R is the side chain of a known penicillin, especially phenoxymethyl or benzyl, and the amino and carboxyl functions are blocked; by 
     A. halogenating the blocked compounds Ia or IIa to produce an imino-halide; 
     B. forming an imino-ether from the imino-halide by treatment with an alcohol; and 
     C. mixing said imino-ether with water or an alcohol to produce 7-aminocephalosporanic acid or 7-amino-3-methyl-3-cephem-4-carboxylic acid. 
     The invention claimed is the use of dicyclohexylamine or diisopropylamine instead of a tertiary amine acid scavenger in step A.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

This invention relates to a more ecologically desirable and safeprocedure for cleaving cephalosporins and then recovering the acidscavenger required in the cleavage process.

2. Description of the Prior Art:

Several processes for the chemical cleavage of cephalosporin C orcertain of its derivatives are described in the patent literature (U.S.Pat. Nos. 3,188,311, 3,234,223, 3,124,576, 3,573,296, 3,573,295 and3,697,515 and British Pat. No. 1,041,985. None of these processes employor teach acid scavengers other than tertiary amines.

SUMMARY OF THE INVENTION

This invention relates to the use of two secondary amine acid scavengersin the cleavage of compounds Ia and IIa to produce 7-ACA or 7-ADCA.

7 -aminocephalosporanic acid (7-ACA) and7-amino-3-methyl-3-cephem-4-carboxylic acid (7-ADCA) are availableintermediates in the preparation of a multitude of semisyntheticcephalosporanic acid antibacterial agents. Commercial supplies of 7-ACAand 7-ADCA are prepared by the chemical degradation of either naturallyoccurring cephalosporanic acids, i.e., cephelosporin C or penicillinsrearranged by the sulfoxide process (thermal rearrangement) to producecompounds such as 7-phenoxyacetamido-3-methyl-3-cephem-4-carboxylicacid.

Most 7-ACA is derived from cephalosporin C (U.S. Pat. No. 3,093,638)which has the structure ##SPC2##

The production of 7-ACA by currently available methods is fraught withdifficulties from the fermentation step to the chemical cleavage ofcephalosporin C.

Because of its highly ionic nature, cephalosporin C is extremelydifficult to harvest by solvent extraction of the fermentation broth.Methods have been devised to improve recovery by the in situ formationof N-acylated cephalosporin C derivatives (see U.S. Pat. No. 3,573,296and 3,573,295), which are then solvent extractable and usable as such orafter purification in the subsequent preparation of 7-ACA.

It was found in U.S. Pat. Nos. 3,473,295 and 3,573,296 that haloformatederivatives and isocyanate derivatives having the formula ##SPC3##

wherein R¹ is --O--R² or --NH--R² in which R² is (lower)alkyl or arylhaving the formula ##SPC4##

in which n is an integer of 1 to 6 and R³ and R⁴ are alike or differentand each is H, Cl, Br, F, NO₂, , (lower)alkyl or (lower)alkoxy can beprepared in situ in whole fermentation broth and then be extracted fromthe aqueous phase by organic solvent extraction. The N- blockedcephalosporin C was then isolated as the sodium salt but the purity wasoften less than desirable. It was subsequently found (as disclosed byour colleague Thomas J. Brooks, Jr. in U.S. application Ser. No.283,887) that N-Carbisobutoxycephalosporin C could be convenientlypurified by recrystallization as the di(dicyclohexylamine) salt in 97%purity.

Subsequent studies showed the di(dicyclohexylamine) salt ofN-carbisobutoxycephalosporin C could be used directly in the silylationstep of the cleavage reaction to block two carboxyl groups, e.g.##SPC5##

and/or possibly some IVa"' consisting of ##EQU2## linked by esterformation to 2 carboxyl groups of 2 molecules of IIIa. For simplicity,formula IVa' is representative of all the possible silyl esters soproduced by the reaction.

The yields of compound IVa using the di (dicyclohexylamine) salt ofcompound IIIa were found to be approximately as good as those obtainedusing a tertiary amine, e.g., triethylamine or dimethylaniline. That isto say, the secondary amine, dicyclohexylamine, did not preventformation of the silyl esters of compound IIIa.

The discovery of this unexpected result stimulated the investigation ofthe possibility of using dicyclohexylamine as the acid scavenger in theformation of the iminohalide derivative of compound Va formed by theinteraction of compound IVa with phosphorous petachloride.

Accordingly, compound IVa was treated with phosphorous pentachloride inthe presence of dicyclohexylamine in a molar ratio of 1:1.25:2.44(compound IVa: PCl₅ : dicyclohexylamine) at about -45°C. Analyticalstudies indicated the formation of compound Va having the structure##SPC6##

Compound Va, in situ was cooled to -60°C and chilled methanol was addedwith stirring to produce the compound VIa, which was identified byanalytical studies, i.e., ##SPC7##

Treatment of VIa with 50% aqueous methanol at -40°C produced 7-ACA in76% yield.

The discovery that it is possible to use a secondary amine as the acidscavenger in this cleavage reaction was a pleasant and unexpectedsurprise.

Chemically, one would expect dicyclohexylamine to react competitivelywith the PCl₅ used therein to produce phosphorous compounds of theformulas, for example, ##EQU3##

If the dicyclohexylamine so reacted with the PCl₅, the PCl₅ would beavailable to form the imino-halide compound Va and the dicyclohexylaminewould be unavailable as an acid scavenger for that HCl generated by thePCl₅ that did react with compound IVa to form compound Va.

It is probable that there is some interaction of the PCl₅ anddicyclohexylamine taking place, but it is either insignificant orreversible and as such has no effect on the main reaction betweencompound IVa and the PCl₅.

A second chemical reaction can occur between secondary amines andimino-halides. The secondary amine is normally expected to react withimino-halides to produce an amidine, e.g., ##EQU4## The amidines soproduced would be stable to hydrolysis and would not produce 7-ACA underthe conditions employed.

Thus the failure of dicyclohexylamine to so react with the imino-halideVa was also an unexpected result.

Subsidiary benefits of this discovery are the commercially desirableones which include:

1. the excellent recovery of dicyclohexylamine from the reactionprocess, thereby resulting in decreased costs and a lesser pollution ofthe environment. 2. a safer process because it means the use of lessvolatile dicyclohexylamine instead of dimethylaniline, a notoriouslytoxic chemical.

Subsequent experiments, as illustrated in the examples, indicate thecleavage reaction works substantially as well using dicyclohexylamine asthe acid scavenger as does the use of a tertiary amine such as pyridine,triethylamine or dimethylaniline. Furthermore, it was subsequently foundthat diisopropylamine can also be used as the acid scavenger. The yieldswith either amine is in the range of 55 to 89% depending upon the molarratios of the reactants so used. The use of dicyclohexylamine appears tohave the advantage over diisopropylamine in that it is more easilyrecovered and purified for recycling in the process.

The process using dicyclohexylamine or diisopropylamine is completelyadaptable to the cleavage of compound having the formula IIa, especiallywhen R is phenoxymethyl or benzyl.

7-aminocephalosporanic acid has the structure ##SPC8##

7-amino-3-methyl-3-cephem-4-carboxylic acid has the structure ##SPC9##

The term "(lower)alkyl" for the purpose of the present invention isdefined as an alkyl group comprised of 1 to 10 carbon atoms, includingfor example, methyl, ethyl n-propyl, isopropyl, n-butyl, isobutyl,t-butyl, n-pentyl, etc., and the like, but especially methyl, ethyl,n-propyl, isopropyl, n-butyl and isobutyl. The terms "(lower)alkoxy" and"halo(lower)alkyl" are also defined as moieties containing 1 to 10carbon atoms.

A preferred embodiment of the instant invention is the process for thepreparation of a compound having the formula ##SPC10##

in which R⁶ is H or acetoxy and R⁵ is OH or the residue of an acidblocking group, which process comprises treating a compound having theformula ##SPC11##

in which R⁶ is H or acetoxy, CO₂ R⁵ is a carboxyl group blocked toconvert it into a group not reacting with the acid halide used forforming the imino-halide, and acyl is the residue of a carboxylic acid;with an acid halide to form an imino-halide, converting the imino-halideinto an imino-ether by means of treating the imino-halide with analcohol and splitting the imino-ether double bond with a compoundcontaining a hydroxy group; the improvement of which comprises usingdiisopropylamine or dicyclohexylamine as the acid scavenger in theimino-halide forming step.

A more preferred embodiment is the process for the preparation of acompound having the formula ##SPC12##

in which R⁶ is H or acetoxy and R⁵ is OH or OY in which Y is alkyl of 1to 10 carbon atoms, a radical of the formula ##SPC13##

in which n is an integer of 0 to 6 and R¹¹ and R¹² are alike ordifferent and each is H, Cl, Br, F, NO₂, (lower)alkyl or (lower)alkoxy,or Y is 2,2,2-trichloroethyl, methoxymethyl and pivaloyloxymethyl; whichprocess comprises treating a compound having the formula ##SPC14##

wherein R⁶ is H or acetoxy, R is the side chain of a known fermentablepenicillin, R⁷ is H, R⁸ is alkanoyl of 2 to 20 carbons, but preferably 2to 6 carbons, or R⁸ is a radical of the formula ##EQU5## in which R¹⁰ isalkyl of 1 to 6 carbons or a group of the formula ##SPC15##

wherein n is an integer of 0 to 6 and R¹¹ and R¹² are alike or differentand each is H, Cl, Br, F, NO₂, (lower)alkyl or (lower) alkoxy, or R⁸ istrichloroacetyl, chloroacetyl, phenylacetyl or benzoyl, or when R⁷ andR⁸ are taken together an o-phthaloyl group; R⁵ is --OY in which Y isalkyl of 1 to 10 carbon atoms, a radical of the formula ##SPC16##

is which n is an integer of 0 to 6 and R¹¹ and R¹² are alike ordifferent and each is H, CL, Br, F, NO₂, (lower)alkyl or (lower)alkoxy;or Y is --CH₂ --CCl₃, --Si(CH₃)₂ Cl, --Si(CH₃)₃ or ##EQU6## with an acidhalide to form an imino-halide, converting the imino-halide into animino-ether by means of treating the imino-halide with an alcohol, andsplitting the imino-ether double bond by the addition of water; theimprovement which comprises using diisopropylamine or dicyclohexylamineas the acid scavenger in the imino-halide forming steps.

A preferred embodiment of the instant invention is the process for thepreparation a compound having the formula ##SPC17##

in which R⁶ is H or acetoxy; which process comprises treating a compoundhaving the formula ##SPC18##

wherein R⁶ is H or acetoxy, R is phenoxymethyl or benzyl, R⁷ is H, R⁸ isalkanoyl of 2 to 6 carbons, a radical of the formula ##EQU7## in whichR¹⁰ is alkyl of 1 to 6 carbons or a group of the formula ##SPC19##

wherein n is an integer of 0 to 6 and R¹¹ and R¹² are alike or differentand each is H, Cl, Br, F, NO₂, (lower)alkyl or (lower)alkoxy, or R⁸ istrichloroacetyl, chloroacetyl, phenylacetyl or benzoyl, or when R⁷ andR⁸ are taken together an o-phthaloyl group and R⁵ is ##EQU8## with anacid halide to form an iminohalide, converting the imino-halide into animino-ether by means of treating the imino-ether with a (lower)alkanol,and splitting the imino-halide double bond by treatment with water; theimprovement of which comprises using diisopropylamine ordicyclohexylamine as the acid scavenger in the imino-halide formingstep.

The most preferred embodiment is the process for the preparation of7-aminocephalosporanic acid from compound XXa in which R⁶ is acetoxy, R⁷is H, R⁸ is carbisobutoxy, ##EQU9## the reaction solvent is methylenechloride, the acid halide is phosphorous pentachloride, the(lower)alkanol is methanol and the acid scavenger is dicyclohexylamine.

Another most preferred embodiment is the process for the preparation of7-amino-3-methyl-3-cephem-4-carboxylic acid from compound XXb in which Ris phenoxymethyl, R⁵ is ##EQU10## the solvent of reaction is methylenechloride, the acid halide is phosphorous pentachloride, the(lower)alkanol is methanol and the acid scavenger is dicyclohexylamine.

In the starting materials XX, 7-N-acyl group is the acyl group of anymono- or dicarboxylic acid, especially the δ-aminoadipoyl group of whichthe free amino and carboxyl groups are blocked.

Groups useful for the blocking of the free amino and carboxyl groupsoccurring in 7-acyl radicals are known in the art, especially from thefield of aminoacids and peptides. It should, however, be noted, that inthe present reaction the whole acyl residue is split off and rejectedand that, therefore, there is no need to use blocking groups which canbe split off after the reaction has been carried out. Useful forblocking the amino group is, for example, a lower alkyl, aryl or acylradical, advantageously a radical which reduces the basicity of theamino group. The aryl radicals may be substituted. Especially suitableare the 2:4-dinitrophenyl, the 2:4:6-trinitrophenyl, the2:4-dinitro-6-methoxy-phenyl, the 4-cyanophenyl and the4-carbomethoxyphenyl radical. Acyl are more especially lower alkanoylradical with one to six carbon atoms, for example acetyl, propionyl,butyryl, also aroyl radicals, such as benzoyl, as well as benzoylsubstituted by nitro, cyano, sulfo groups, halogen atoms, lower alkyl orlower alkoxy groups, and preferably N:N-phthaloyl; further, aryloweralkanoyl radicals, such as phenylacetyl, or the benzenesulfonyl ortoluenesulfonyl radical may be used for blocking the amino group. Theamino groups can also be blocked by protonation.

The free carboxyl group is, for instance, blocked by esterification. Asin the case of amino groups occurring in the acyl radical, also acarboxyl group occurring in the acyl radical can be blocked in suitableway and there is no critical point in this regard as the whole acylresidue is split off in the reaction. Thus, esters with hydroxycompounds can be used, for example, with alcohols such as unsubstitutedor substituted alcohols or phenols. In most cases, it will be preferredto start with compounds in which a carboxyl group occurring in the7-acyl residue is blocked in the same way as the carboxyl group in4-position of the dihydrothiazine ring. Hydroxy compounds suitable forthat purpose are indicated for illustration below. It is, however, alsopossible, especially in the case of the δ-aminoadipolyl residue, toblock the amino and carboxyl group together, for example by reactionwith isocyanates or isothiocyanates with formation of a hydantoin orthiohydantoin ring.

If, in the starting material of formula XX, the 7-acyl group is theblocked δ-aminoadipoyl group, the compound is derived from CephalosporinC. Other 7-acylaminocephalosporanic acids or derivatives thereof,respectively, can also be used as starting materials for the newprocess. Thus, the acyl group can be an aliphatic, aromaticheterocyclic, araliphatic or heterocyclicaliphatic carboxylic acidradical, especially the acyl radical of naturally occurring7-acylaminocephalosporanic acids and 6-acylaminopenicillanic acids [thatcan be prepared starting from naturally occurring cephalosporins orpenicillins], for example cephalosporin C or 6-(δ-amino-adipoyl)aminopenicillanic acid, penicillin G, V, F, dihydro-F, K, X or O. In thestarting compounds of formula XX, the carboxyl group occurring in4-position is blocked during the reaction with the imino-halide formingagent. The purpose of the blocking is to avoid the carboxyl group beinghalogenated by that agent, for instance phosphorous pentachloride. Asblocking groups, therefore, any compound may be used, which converts thecarboxyl group into a group not reacting with that agent. If the7-desacylated compound is to be isolated in the form of the freecarboxylic acid, a blocking group should be used which can be split offwithout destruction of the cephalosporin nucleus. Such blocking groupsare, for instance, ester groups that can be split in an acidic orneutral or weakly basic (up to pH9) reaction medium, for instance, byreduction, solvolysis, for instance acid hydrolysis or photolysis.Advantageously, the carboxyl group is esterified with hydroxy compoundsknown in the field of aminoacids and peptides to be readily eliminablefrom the ester especially in a non-alkaline medium. Such hydroxycompounds derive from elements of the fourth group (IV A) of theperiodic system having an atom weight of at most 120, for instance fromcarbon, silicon, germanium or tin. For illustration, methanolsubstituted by at least one phenyl group which phenyl may be substitutedby one or more substituents selected from the group consisting ofhalogen atoms such as chlorine, bromine, fluorine, iodine, lower alkyl,lower alkoxy, especially methoxy, or the nitro group, for instance,benzylalcohol, diphenylmethanol, triphenylmethanol,para-methoxyphenyl-methanol 3,5-dimethoxy-benzylalcohol,di-paramethoxyphenyl-methanol, para-nitrobenzylalcohol,2,4,6-trimethylbenzylalcohol, 3,4-dimethoxy-6-nitro-benzylalcohol,α-phenyl-α-(3,4-dimethoxy-6-nitro-phenyl)-methanol, α-methyl-α-(3,4-dimethoxy-6-nitrophenyl)-methanol, further methanol substituted bythree lower alkyl groups such as tertiary butanol, tertiary amylalcoholor ethanol, substituted by 3 halogen atoms in 2-position, e.g.trichloroethanol, tribromethanol; further 2-iodoethanol,tetrahydropyranol, stannylalcohol.

As mentioned above, the blocking group has to be present only during thestep of formation of the imide halide. After that step it can be splitoff, if desired. This splitting can be effected by solvolysis, forinstance with water or alcohols, if desired in an acidic or weaklyalkaline medium, or by reduction, for instance with hydrogen in thepresence of a catalyst or with metals such as zinc, or finally, byphotolysis, preferably in a polar medium.

A blocking ester group can also be retained if it is split enzymaticallyin the tissue on administration of the compound.

Agents forming imido-halides are, more especially acid halides,particularly chlorides, which are derived from phosphorus, sulfur,carbon or their oxygen acids, for example phosphorus oxychloride,phosphorus pentachloride, phosphorus trichloride, thionyl chloride,phosgene and oxalyl chloride

The imino-halide is reacted with an alcohol to form an imino-ether.Alcohols are, for example, lower alkanols such as ethanol, n-propanol,isopropanol n-butanol, especially methanol, phenyl lower alkanols, forinstance, benzyl alcohol, or (lower)alkyldiols, such as propylene orethylene glycol. The iminoether is an intermediate which need not beisolated but can be split in the same reaction medium.

The splitting of the C=N double bond of the iminoether to form thecompound XXX is carried out with a compound containing a hydroxyl groupsuch as water or an alcohol, for instance, that alcohol used for formingthe iminoether, or with a mixture of alcohol with water, preferably at apH from 0 to 4.

Other examples of what acyl can represent in compounds XX are theradical having the formula

    R.sub.2 (CH.sub.2).sub.n CO

in which n represents an integer of 0 to 4, preferably 1, and in which aCH₂ -group, especially in α-position may be substituted, for instance byamino, halogen, lower alkoxy, cyan, nitro or carboxyl, and R₂ representsan unsubstituted or substituted aryl, cycloalkyl, or heterocyclylradical or an aryloxy, arylthio, cycloalkoxy, heterocyclyloxy orheterocyclylthio radical, the aryl or heterocyclyl radicals beingmonocyclic or dicyclic, for example 2:6-dimethoxy-benzoyl,tetrahydronaphthoxyl, 2-methoxynaphthoyl, 2-ethoxy-naphthoxyl,3-pyridyl-benzoyl, phenylacetyl, phenylglycyl, phenylalanyl,phenylcyanacetyl, p-chlorophenyl-cyanacetyl, phenoxyacetyl,S-phenyl-thioacetyl, S-bromophenylthioacetyl, α-phenoxypropionyl,β-phenoxypropionyl, α-phenoxy-phenylacetyl, α-methoxyphenylacetyl,α-methoxy-3:4-dichlorophenyl-acetyl, pyridyl(3)-acetyl,pyridyl(20)-acetyl, 1-methyl-imidazolyl(2)-thioacetyl,1,2,4-triazolyl(3)-thioacetyl, thiolinyl(2)-thioacetyl,imidazolinyl(2)-thioacetyl, 1-methylimidazoly(1)-acetyl,benzyloxy-carbonyl, S-benzylthioacetyl, S-benzylthiopropionyl,hexahydrobenzyloxycarbonyl, cyclopentanoyl, cyclohexanoyl,2-thienylacetyl, 2-thienyl-cyanacetyl, 3-thienylacetyl, 2-furylacetyl,2-indoylacetyl, 2-phenyl-5-methyl-isoxazoly-carbonyl,2-(2'-chlorophenyl)-5-methyl-isoxazolyl carbonyl, indenylcarbonyl, or aradical of the formula

    C.sub.n H.sub.2n.sub.+1 CO or C.sub.n H.sub.2n.sub.-1 CO

in which n represents an integer of 1 to 7, and the chain is straight orbranched and, if desired, is interrupted by an oxygen atom or a sulfuratom or is substituted, for instance, by halogen, cyan, carboxy,carbalkoxy, lower alkoxy, nitro or amino, for example, a propionyl,butyryl, hexanoyl, oxtanoyl, butylthioacetyl, acrylyl,α-cyano-β-dimethyl-acroyl, crotonyl, 2-pentenoyl, allylthioacetyl,chloroacetyl, β-bromopropionyl, dichloroacetyl, dibromacetyl,difluoroactyl, ethoxycarbonylacetyl, dimethoxycarbonylacetyl,cyanacetyl, α-cyanopropionyl, nitroacetyl, aminoacetyl, orα-carboxylpropionyl radical.

EXAMPLES EXAMPLE 1 Preparation of 7-aminocephalosporanic acid viadicyclohexylamine

N-Carbisobutoxycephalosporin C di(dicyclohexylamine) salt (IIIa, 10 g.)was added to 150 ml of dry methylene chloride, followed by 3.5 ml. ofdichlorodimethylsilane over a 10 minute period with stirring. Twoadditional 10 gram portions of IIIa were added to the resultant slurry,followed each time by 3.5 ml of dichlorodimethylsilane. The final slurrywas aged for 30 minutes with vigorous stirring and then brought to 240ml volume with additional methylene chloride. A sample of the slurry wasdetermined to be the desired disilyl ester ofN-carbisobutoxycephalosporin C (IVa).

A one-third portion of the slurry (11.38 mmoles of the IVa ester) wastreated with 5.73 ml (27.77 mmoles) of dicyclohexylamine. The resultantslurry was cooled to -45° C and 3 g. (14.23 mmoles) of finely groundPCl₅ was added with stirring and continued cooling. The temperaturesurged to -35° C and the chlorination slurry was cooled back to -40° Cand held there for 15 minutes. The chlorination mix was cooled to -60° Cand 40 mls of precooled methanol (-70° C) was added all at once. Themixture was aged with stirring for 120 minutes at -40° C.

Ice cold 50% aqueous methanol (16.8 ml) was added to the -40°C mixture.The temperature rose to -10° C and was held in the range of -10 to -40°C for 25 minutes. The mixture was warmed to 0° C and dripped into 140 mlof methanol and 28 ml of water keeping the mixture at constant pH 3.6with NH₄ OH.

The 7-ACA slurry so produced was stirred for 60 minutes at 5 to 10° C,then filtered and washed with ice cold water and methanol. The yield was2.37 g. of 97% pure 7-ACA (76.7%).

Concentration in vacuo or at atmospheric pressure of the mother liquorsleaves a post residue consisting of essentially dicyclohexylaminehydrochloride, water and unreacted or decomposed cephalosporin Cby-products. Basification of the pH to about 9 with sodium hydroxide,followed by physical separation of the two layers produces essentiallypure dicyclohexylamine in about 85-95% recofery of theory.

EXAMPLE 2 Preparation of 7-ACA via dicyclohexylamine

Compound IIIa (40 g, 45.55 mmoles) was suspended in dry methylenechloride (400 ml) followed by the addition of dichlorodimethylsilane(14.0 ml, 14.89 g, 116.03 mmoles) at 25° under a nitrogen atmosphere.The slurry was stirred at 25° for 1 hour and cooled to -40°.Dicyclohexylamine (45.36 ml, 41.28 g. 227.66 mmoles) dissolved inmethylene chloride to a total volume of 120 mls was added slowly to theester slurry at -40°. After 20 ml of the amine was added, finely groundphosphorous pentachloride (20.86 g, 100.16 mmoles) was added in oneportion to the slurry. The temperature rose 5°-8° during the addition ofthe phosphorous pentachloride. The remainder of the amine solution wasadded slowly over a 30-40 minute period and chlorination was allowed toproceed for 2 hours at -30 to -40°. The slurry was cooled to -50° andprecooled (-60°) methanol (46.2 ml., 36.5 g, 1.138 moles) was added over15-20 minutes maintaining the temperature below -40°. Methylation wasallowed to proceed for 1 1/2 hours at -40°. Methanol (150 ml) wasrapidly added and the mixture stirred at -35 to -40° for 0.5 hours.Water (25.0 ml) was added at -35° and the mixture stirred at thistemperature at -35° for 1 hour. The slurry was warmed to 0°-5°. Water(30.0 ml) and methanol (200 ml) were added until all of thedicyclohexylamine hydrochloride dissolved. A portion of the batch (0.33volume) was cyrstallized by pH adjustment with 6N ammonium hydroxide at0°-5°. The remainder of the solution was added to the 7-ACA slurry overa 30-40 minute period maintaining the pH at 3.4-3.6. After the addition,the slurry was stirred for 1 hour at 0°-5° holding the pH at 3.6. Theslurry was filtered, washed with methanol and dried at 40°-50°: 9.43 g(76%). Infrared and NMR spectra were consistent for structure. The yieldcorrected for input cephalosporin potency and output 7-ACA potency is10.28 g., 83%. The material assayed at 966 mcg/mg by chemical assay.

EXAMPLE 3 Preparation of 7-ACA via diisopropylamine

Compound IIIa (20.0g, 22.77 mmoles) was suspended in dry methylenechloride (200 ml) followed by the addition of dichlorodimethylsilane(7.0 ml, 7.49 g, 58.02 mmoles) at 25° C under a nitrogen atmosphere. Theslurry was stirred at 25° C for 1 hour and cooled to -40° C.Diisopropylamine (15.96 ml, 11.52 g, 113.86 mmoles) dissolved inmethylene chloride to a total volume of 60 ml was added slowly to theester slurry at -40° C. After 10 ml of the amine was added, finelyground phosphorus pentachloride (10.43 g, 40.98 mmoles) was added in oneportion to the slurry. The temperature rose 5°-8° during the addition ofthe phosphorus pentachloride. The remainder of the amine solution wasadded slowly over a 30-40 minute period and chlorination was allowed toproceed for 2 hours at -30° to -40° C. The slurry was cooled to -50° Cand precooled (-60°)methanol (23.1 ml, 18.3 g, 569.3 mmoles) was addedover a 15-20 minute period maintaining the temperature below -40° C.Methylation was allowed to proceed for 1 1/2 hours at -40° C. Methanol(50 ml) was rapidly added and the mixture stirred at -35° to -40° for0.5 hours. Water (12.0 ml) was added at -35°C and the mixture stirred atthis temperature for 1 hour. The slurry was warmed to 0°-5°. Water (15.0ml) and methanol (75 ml) were added until all of the dicyclohexylaminehydrochloride dissolved. A portion of the batch (0.33 volume) wascrystallized by pH adjustment with 6N ammonium hydroxide at 0°-5°. Theremainder of the solution was added to the 7-ACA slurry over a 30-40minute period maintaining the pH at 3.4-3.6. After the addition, theslurry was stirred for 1 hour at 0°-5° holding the pH at 3.6. The slurrywas filtered, washed with methanol and dried at 40°-45°: 4.92 g, 79.4%.Infrared and NMR spectra were consistent for structure. The yieldcorrected for input cephalosporin potency is 5.15 g, 83%.

EXAMPLE 4 Preparation of 7-ACA using dicyclohexylamine

Substitution in the procedure of example 2 for the amounts of compoundIIIa, PCl₅, CH₂ Cl₂, dicyclohexylamine (DCHA), dichlorodimethylsilane(DDS) and methanol used therein of the amounts indicated in thefollowing chart produced 7-ACA in the indicated yields. Each experimentwas modified in some manner as to the order or mode of addition of theDCHA and/or PCl₅ as footnoted below the chart.

                                      TABLE                                       __________________________________________________________________________    Compound                            Actual                                                                              Theoretical  Chem.                  IIIa    PCl.sub.5                                                                               DCHA Methanol                                                                             CH.sub.2 Cl.sub.2                                                                   Yield(g)                                                                            Yield  % Yield*                                                                            Potency                __________________________________________________________________________    No. 1 20.0 g                                                                          5.22, 1.1eq.                                                                           6.81 ml                                                                             23.11 ml.                                                                            170 ml.                                                                             no yield                                                   1.5 eq.            obtained                                  No. 2 20.0 g                                                                          5.22, 1.1eq.                                                                           13.61 ml                                                                            23.11 ml.                                                                            170 l.                                                                              2 gms.                                                                              6.2 gms.                                                                             32%   --                                      3.0 eq.                                                      No. 3 20.0 g                                                                          10.43, 2.2eq.                                                                          22.68 ml                                                                            23.11 ml.                                                                            170 ml.                                                                             5.52  6.2    89%   840 mcg/mg.                             5.0 eq.                                                      No. 4 20.0 g                                                                          14.23, 3.0eq.                                                                          27.22 ml                                                                            23.11 ml.                                                                            170 ml.                                                                             3.48  6.2     56.1%                                                                              985 mcg/mg.                             6.0 eq.                                                      No. 5 20.0 g                                                                          10.43g, 2.2eq.                                                                         22.68 ml                                                                            23.11 ml.                                                                            170 ml.                                                                             5.53  6.2    89%   983/mcg/mg.                             5.0 eq.                                                      No. 6 20.0 g                                                                          10.43g, 2.2eq.                                                                         22.68 ml                                                                            23.11 ml.                                                                            170 ml.                                                                             5.23  6.2    85%   965 mcg/mg.                             5.0 eq.                                                      No. 7 40.0 g                                                                          20.86g, 2.2eq.                                                                         45.36 ml                                                                            46.22 ml.                                                                            400 ml.                                                                             8.8   12.4   71%   954 mcg/mg.                             5.0 eq.                                                      No. 8 20.0 g                                                                          10.43, 2.2eq.                                                                          22.68 ml                                                                            23.11 ml.                                                                            170 ml.                                                                             5.14  6.2    83%   962 mcg/mg.                             5.0 eq.                                                      No. 9 40.0 g                                                                          20.86, 2.2eq                                                                           45.36 ml                                                                            46.22 ml.                                                                            400 ml.                                                                             10.64 12.4   86%   966 mcg/mg.                             5.0 eq.                                                      __________________________________________________________________________    No. 1                                                                              PCl.sub.5 added in solution as rapidly as possible, immediately               followed by DCHA addition.                                               No. 2                                                                              PCl.sub.5 added in solution as rapidly as possible, immediately               followed by DCHA addition.                                               No. 3                                                                              PCl.sub.5 in solution and base in solution added over a 20 minute             period simultaneously.                                                   No. 4                                                                              Same as No. 3.                                                           No. 5                                                                              Base suspended in CH.sub.2 Cl.sub.2 (total volume=60 mls) 16-17% or           10 mls. DCHA added, then solid, finely                                        ground PCl.sub.5, then continue dripping in base over a 20 minute             period.                                                                  No. 6                                                                              Same as No.5.                                                            No. 7                                                                              Same as No.3.                                                            No. 8                                                                              Same as No.5.                                                            No. 9                                                                              Same as No.5.                                                            __________________________________________________________________________     *Not corrected for purity of starting material or product.               

EXAMPLE 5 Preparation of N-Carbisobutoxycephalosporin C di(dicyclohexylamine) salt from cephalosporin C whole broth

One kg of cephalosporin C whole broth was adjusted to pH 2.0 with 30%sulfuric acid. Filter aid was added and the slurry was filtered througha precoated Buchner filter. The cake was washed with water to a filtrateand wash volume of 1500 ml.

One-fourth volume (375 ml) of acetone was added to the filtrate andwashes and the mixture was adjusted to pH 8.0-8.2 with 10% NaOH whilecooling to 0°-5°C.

While maintaining the pH at 8.0 with 10% NaOH on an automatic titrator,15 ml of isobutyl chloroformate dissolved in 45 ml of acetone dried overmolecular sieves was dripped in during 60-minutes time. The mixture washeld at pH 8.0 for another 30 minutes at 0°-5° C. Assays showed <2%residual cephalosporin C and 94% yield of N-CarbisobutoxycephalosporinC.

1500 ml of methylisobutylketone (MIBK) was added to the acylatedmixture. The pH was adjusted to 2.0 with 30% sulfuric acid and theemulsion was stirred for 10 minutes at 0°-5° C. The layers were thenseparated using a DeLaval centrifuge. The aqueous layer was extractedagain with 500 ml of fresh MIBK for 5 minutes and separated in thecentrifuge. The two rich MIBK extracts were combined and polishfilteredthrough filter aid. The clear filtrate was vacuum concentrated at 40° Cto 400 ml. To the 400 ml of concentrate, 25 ml of water was added. ThepH was adjusted to 4.5 with dicyclohexylamine and the mixture wasstirred for 1-2 hours at 25°-30°C during which time a thick slurry ofcrystals was obtained. The pH was then adjusted to 5.0-6.0 withdicyclohexylamine and the slurry was stirred another 2 hours at25°-30°C. The slurry was then filtered and the crystals washedthoroughly with MIBK and then with acetone. After vacuum drying at 45°Cfor 16 hours, the yield of dry, crystalline N-carbisobutoxycephalosporinC di (dicyclohexylamine) salt was 75% of theory based on the whole brothassay.

Variations in the above procedure have given equivalent or improvedresults. Successful variations have been adjustment of whole broth to pH4 instead of 2 with sulfuric acid, adjustment of whole broth to pH 4with oxalic acid, and crystallization of concentrate at pH 5.0 or 5.5instead of 6.0.

EXAMPLE 6 Preparation of 7-aminocephalosporanic acid from monosodiumN-carbisobutoxycephalosporin C and dicyclohexylamine (see U.S. Pat. No.3,573,296 for starting material)

Sodium N-carbisobutoxycephalosporin C (13.5 g.) , 90 ml of methylenechloride and 5.0 ml of dicyclohexylamine are mixed together.Dichlorodimethylsilane (6.2 ml) is added with stirring at about roomtemperature and stirring is continued for about 30 minutes. The slurryis then cooled to -60° C and 12 grams of phosphorus pentachloridedissolved in 100 ml of methylene chloride is added. An additional 11.0of dicyclohexylamine is added while the temperature is kept below -40°C.The temperature is lowered to below -60°C and 60 ml of methanol (-70°C)is added slowly. The temperature is kept below -40°C. Subsequently, 55ml of water is added slowly, allowing the temperature to rise. Themixture is kept cooled to about 0°C. Ammonium hydroxide is added slowlyto raise the pH to about 3.6. The precipitate which forms is collectedby filtration is 7-ACA.

EXAMPLE 7 Preparation of 7-ACA from N-phthaloylcephalosporin C-dibenzylester

N-Phthaloylcephalosporin C-dibenzyl ester (11.38 mmoles) is dissolved in50 ml of methylene chloride and cooled to -45° C. Dicyclohexylamine(5.73 ml., 27.77 mmoles) is added followed by 3 g (14.23 mmoles) offinely ground PCl₅ with stirring and continued cooling below -45°C. Thechlorination mix is cooled to -60°C after about 15 minutes, and 40 mlsof precooled methanol (-70°C) is added all at once. Stirring iscontinued about 2 hours.

Ice cold 50% aqueous methanol is added (16.8 ml) and the temperature isheld below -10° C for 25 minutes. The mixture is warmed to about 0°C andadjusted to pH 3.3 with ammonium hydroxide. The organic solvents areremoved in vacuo and the aqueous phase is extracted with benzene andethyl acetate (2:1). The organic phase is extracted with 3% aqueousphosphoric acid and this solution is adjusted to pH 8.5 and thenextracted with ethyl acetate. The ethyl acetate phase containing the7-aminocephalosporanic acid benzyl ester is dried over sodium sulfate,filtered and taken to dryness to yield the desired7-aminocephalosporanic acid benzyl ester.

EXAMPLE 8 Preparation of 7-ACA and 7ADCA from various blockedcephalosporin C derivatives

Substitution in the general procedure of example 7 for theN-phthaloylcephalosporanic C dibenzyl ester used therein of equimolarquantities of

1 N-phenylacetylcephalosporin C-dibenzyl ester,

2. N-carbobenzoxycephalosporin D-dibenzyl ester,

3. N-2,4-dinitrophenylcephalosporin C-dibenzyl ester,

4. N-benzoylcephalosporin C-dibenzyl ester,

5. N-phthaloylcephalosporin C-di-(para-methoxybenzyl ester,

6. N-phthaloylcephalosporin C-dibenzhydryl ester,

7. N-phthaloylcephalosporin C-di (tetrahydropyron-2-yl ester)

8. N-2,4-dinitrophenylcephalosporin C-di (paranitrophenyl ester),

9.7-[4-(1-phenyl-2-thiono-5-oxoimidazoolidine-4-yl)-butyryl]aminocephalosporanicacid methyl ester,

10. 7-(phenylacetamido)cephalosporanic acid benzhydryl ester,

11. 7-(phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid benzhydrylester,

12. 7-(phenylacetamido)-3-methyl-3-cephem-4-carboxylic acidmethoxymethyl ester,

13. N-phthaloylcephalosporin C di (trichloroethylester), or

14. 7-(phenoxyacetamido)-3-methyl-3-cephm-4-carboxylic acidmethoxymethyl ester

produces respectively

1'. 7-aminocephalosporanic acid benzyl ester,

2'. 7-aminocephalosporanic acid benzyl ester,

3'. 7-aminocephalosporanic acid benzyl ester,

4'. 7-aminocephalosporanic acid benzyl ester,

5'. 7-aminocephalosporanic acid p-methoxybenzyl ester,

6'. 7-aminocephalosporanic acid benzhydryl ester,

7'. 7-aminocephalosporanic acid tetrahydropyran-2-yl ester,

8'. 7-aminocephalosporanic acid p-nitrophenyl ester,

9'. 7-aminocephalosporanic acid methyl ester,

10'. 7-aminocephalosporanic acid benzhydryl ester,

11'. 7-amino-3-methyl-3-cephem-4-carboxylic acid benzhydryl ester,

12'. 7 -amino-3-methyl-3-cephem-4-carboxylic acid methoxymethyl ester,

13'. 7-aminocephalosporanic acid trichloroethyl ester, and

14'. 7-amino-3-methyl-3-cephem-4-carboxylic acid methoxymethyl ester.

EXAMPLE 9 Preparation of 7-ACA via silyl ester and dicyclohexylamine ordiisopropylamine

N-Carbisobutoxycephalosporin C (34.14 mmoles) as the free acid is addedto 150 ml of methylene chloride, followed by dicyclohexylamine (75mmoles) or diisopropylamine (75 mmoles), subsequently followed by 10.5ml of dichlorodimethylsilane over a ten minute period with stirring. Theresultant slurry is aged 30 minutes with vigorous stirring and thenbrought to 240 ml with additional methylene chloride.

A one-third portion of the slurry is cooled to 45°C and then treatedwith 27.77 mmoles of dicyclohexylamine or diisopropylamine (the same oneas is used above in the silyl ester formation). The PCL₅, methanol andwater steps are conducted in a manner identical to that used in example1 to produce 7-ACA.

EXAMPLE 10 Preparation of 7-ACA from various blocked cephalosporin Cderivatives

Substitution in the procedure of Example 9 for theN-carbisobutoxycephalosporin C used therein of an equimolaar quantity of

1. N-phenylacetylcephalosporin C,

2. n-carbobenzoxycephalosporin C,

3. n-benzoylcephalosporin C,

4. n-phthaloylcephalosporin C,

5. n-2,4-dinitrocephalosporin C,

6. n-chloroacetylcephalosporin C,

7. n-acetylcephalosporin C,

8. n-(n'-butylcarbanoyl)cephalosporin C,

9. n-(n'-p-methylphenylcarbanoyl)cephalosporin C,

10. n-(n'-isopropylcarbanoyl)cephalosporin C,

11. n-(n'-isobutylcarbanoyl)cephalosporin C,

12. n-(n'-phenylcarbanoyl)cephalosporin C,

13. n-trichloroacetylcephalosporin C produces 7-ACA.

EXAMPLE 11 Preparation of 7-ADCA

7-(Phenoxyacetamido)-3-methyl-3-cephem-4-carboxylic acid (11.38 mmoles)is dissolved in 80 ml of methylene chloride. Dicyclohexylamine ordiisopropylamine (13 mmoles) is added with stirring and 1.75 ml ofdichlorodimethylsilane is added. After stirring for 30 minutes, themixture is cooled to -45° C and an additional 27.77 mmoles of the sameamine as used above is added followed by 3 g of finely powdered PCl₅.

The remaining steps of the reaction and workup are identical to those inexample 1 to produce 7-amino-3-methyl-3-cephem-4-carboxylic acid.

EXAMPLE 12 Preparation of 7-ADCA

Substitution in the procedure of example 11 for the7-(phenoxyacetamido)-3-methyl-3-cephem-4-carboxylic acid used therein ofan equimolar quantity of7-(phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid produces 7-ADCA.

We claim:
 1. In the process for the preparation of a compound having the formula ##SPC20##in which R⁶ is H or acetoxy and R⁵ is OH or the residue of an acid blocking group, which process comprises treating a compound having the formula ##SPC21## in which R⁶ is H or acetoxy, CO₂ R⁹ is a carboxyl group blocked to convert it into a group not reacting with the acid halide used for forming the imino-halide, and acyl is the residue of a carboxylic acid; with an acid halide to form an imino-halide, converting the imino-halide into an imino-ether by means of treating the imino-halide with an alcohol and splitting the imino-ether double bond with a compound containing a hydroxy group; the improvement of which comprises using diisopropylamine or dicyclohexylamine as the acid scavenger in the imino-halide forming step.
 2. A process of claim 1 for the preparation of a compound having the formula ##SPC22##in which R⁶ is H or acetoxy, and R⁵ is --OH or --OY in which Y is alkyl of 1 to 10 carbon atoms, a radical of the formula ##SPC23## in which n is an integer of 0 to 6 and R¹¹ and R¹² are alike or different and each is H, Cl, Br, F, NO₂, (lower)aklyl or (lower)alkoxy, or Y is 2,2,2-trichloromethyl, methoxymethyl or pivaloyloxymethyl; which process comprises treating a compound having the formula ##SPC24## wherein R⁶ is H or acetoxy, R is the side chain of a known fermentable penicillin, R⁷ is H, R⁸ is alkanoyl of 2 to 20 carbons, but preferable 2 to 6 carbons, or R⁸ is a radical of the formula ##EQU11## in which R¹⁰ is alkyl of 1 to 6 carbons or a group of the formula ##SPC25## wherein n is an integer of 0 to 6 and R¹¹ and R¹² are alike or different and each is H, Cl, Br, F, NO₂, (lower)alkyl or (lower)alkoxy, or R⁸ is trichloroacetyl, chloroacetyl, phenylacetyl or benzoyl, or when R⁷ and R⁸ are taken together an o-phthaloyl group; R⁵ is --OY in which Y is alkyl of 1 to 10 carbon atoms, a radical of the formula ##SPC26## in which n is an integer of 0 to 6 and R¹¹ and R¹² are alike or different and each is H, Cl, Br, F, NO₂, (lower)alkyl or (lower)alkoxy; or Y is --CH₂ --CCl₃, methoxymethyl, pivaloyloxymethyl, ##EQU12## or -Si(CH₃)₃ ; with an acid halide to form an imino-halide, converting the imino-halide into an imino-ether by means of treating the imino-halide with an alcohol, and splitting the imino-ether double bond by the addition of water; the improvement of which comprises using diisopropylamine or dicyclohexylamine as the acid scavenger in the imino-halide forming step.
 3. A process of claim 1 for the preparation of a compound having the formula ##SPC27##in which R⁶ is H or acetoxy; which process comprises treating a compound having the formula ##SPC28## wherein R⁶ is H or acetoxy, R is phenoxymethyl or benzyl, R⁷ is H, R⁸ is alkanoyl of 2 to 6 carbons, a radical of the formula ##EQU13## in which R¹⁰ is alkyl of 1 to 6 carbons or a group of the formula ##SPC29## wherein n is an integer of 0 to 6 and R¹¹ and R¹² are alike or different and each is H, Cl, Br, F, NO₂, (lower)alkyl or (lower)alkoxy; or R⁸ is trichloroacetyl, chloroacetyl, phenylacetyl or benzoyl, or when R⁷ and R⁸ are taken together an o-phthaloyl groupl and R⁵ is ##EQU14## with an acid halide to form an iminohalide, converting the imino-halide into an imino-ether by means of treating the imino-ether with a (lower)alkanol, and splitting the imino-ether double bond by treatment with water; the improvement of which comprises using diisopropylamine or dicyclohexylamine as the acid scavenger in the imino-halide forming step.
 4. The process of claim 3 for the preparation of 7-aminocephalosporanic acid from compound XXa in which R⁶ is acetoxy, R⁷ is H, R⁸ is carbisobutoxy, R⁵ is ##EQU15## the solvent of reaction is methylene chloride, the acid halide is phosphorus pentachloride, the (lower)alkanol is methanol and the acid scavenger is dicyclohexylamine.
 5. The process of claim 3 for the preparation of 7-amino-3-methyl-3-cephem-4-carboxylic acid from compound XXb in which R is phenoxymethyl, R⁵ is ##EQU16## the solvent of reaction is methylene chloride, the acid halide is phosphorus pentachloride, the (lower)alkanol is methanol and the acid scavenger is dicyclohexylamine.
 6. The process of claim 1 wherein the temperature is maintained below -20°C. during the formation of the imino-halide and its subsequent conversion to the imino-ether.
 7. The process of claim 1 wherein the temperature is maintained below -40°C. during the formation of the imino-halide and its subsequent conversion to the imino-ether.
 8. The process of claim 4 wherein the temperature is maintained below -20°C. during the formation of the imino-halide and its subsequent conversion to the imino-ether.
 9. The process of claim 4 wherein the temperature is maintained below -40°C. during the formation of the imino-halide and its subsequent conversion to the imino-ether.
 10. The process of claim 5 wherein the temperature is maintained below -20°C. during the formation of the imino-halide and its subsequent conversion to the imino-ether.
 11. The process of claim 5 wherein the temperature is maintained below -40°C. during the formation of the imino-halide and its subsequent conversion to the imino-ether. 